Subsea manifold system

ABSTRACT

A modular, subsea hydrocarbon production hub 36 comprises a primary manifold 22 and a plurality of co-located extension structures 26, 30, 34. The primary manifold 22 has first connections 23 for connection a top-side facility 21, second connections 27, 35 for connection to at least one extension structure 26, 34, and third connections 25 for connection to at least one well 24. The extension structures 26, 30, 34 may comprise a secondary manifold 26, 30, having first connections 27, 31 for connection to the primary manifold 22 or another secondary manifold 26, 30, second connections 31 for connection to at least one further extension structure 26, 30, 36, and third connections 28, 31 for connection to further wells 29, 32. The extension structures 26, 30, 34 may also comprise one or more functional units, such as a pumping unit 34 or a separator unit 51.

The present invention relates to a subsea hydrocarbon production hub,and to a subsea hydrocarbon production system incorporating such a hub,which are particularly useful when oil or gas is to be produced from aplurality of fields where at least one is a remote “satellite” field.

It is well-known that when hydrocarbons (oil and/or gas) are to beproduced from a sub-sea reservoir, a top-side facility, such as aproduction platform or vessel is provided on the surface and well-headis provided on the sea bed. The well-head is located at the top of thewell, through which oil and/or gas may flow from the undergroundreservoir. The well-head is equipped to control the well and has valveand arrangements to prevent leakage from the reservoir.

The well-head is connected to the top-side facility by means of aproduction and/or injection flow line running along the sea bed, oftenfor tens of kilometers, and a riser extending upwardly to the top-sidefacility, also referred to as a platform. Through these, the oil/gasflows to the top-side facility. Also, from the top-side facility, risersfor gas lift, gas injection or water injection are connected to thewell-head, either via subsea manifolds or directly to the dedicatedwells.

In addition, dedicated umbilicals provide power, control andcommunications, as well as the supply of chemicals, such as hydraulicfluids and MEG (mono ethylene glycol), which is used as anti-freeze toprevent the formation of hydrates.

There will typically be a number of well-heads grouped comparativelyclose together. Rather than having separate risers leading to each, amanifold is normally provided on the sea bed. This will have risersconnecting it to the top-side facility to provide thepreviously-mentioned services. In turn, there are separate connectionsfrom the manifold to each of a plurality of well-heads. One example ofsuch a manifold system is disclosed in US 2011/0132615.

Another known situation is for a so-called satellite field to bedeveloped and produced from the same topside facility. When this is tobe done, it can either be achieved by a daisy-chained solution via othertemplates or by connecting each new satellite field directly to thetopside facility. The conventional arrangement is to provide a so-calledriser base in association with each wellhead and for the riser base tobe connected to the topside facility.

FIG. 1 illustrates such a conventional arrangement where a topsidefacility, in this case the platform, is connected to a standard manifoldand to a number of satellite fields.

Referring to that figure, the platform 1 is shown schematically ashaving two regions, 2 and 3. Region 2 provides for connection tostandard manifold 4 by means of umbilical 5 which includes variousconduits. (In the diagram, C indicates conduits for control, power andfluids (hydraulic, chemicals and barrier fluids). WI indicates water orgas injection, and LP/HP indicate low pressure/high-pressure productionrespectively.) Manifold 4 is in turn connected to a number of wells 6(shown here as nos. 1, 2 and 3) by means of connectors 7.

Platform 1 also has a region 3 for connection to satellite fields. Thesefields will typically have been developed subsequent to the initialfields. The satellite fields are shown adjacent to the other fields inthe figure, but in reality they will be dispersed over a large area ofthe seabed, often tens of kilometers away. Each satellite field has ariser base 8, 9, 10 connected to the platform by means of risers andumbilicals 11, 12, 13. The riser bases are in turn connected to varioussatellite fields 14, 15 and 16 by means of connections 17, 18 and 19.

It will be understood from the figure that each satellite field normallyrequires dedicated riser(s) between the satellite field and the topsidefacility, which each must include production lines and provide forinjection of gas and water. In addition, there must be umbilical(s),providing conduits for control, power, MEG and various fluids.Accordingly, between two and four riser slots are needed at the topsidefacility for each satellite field.

Taking these factors together, the result is that for each single newfield, very significant new costs are involved. Whilst these costs maybe economically justifiable where the satellite fields in questioncontain significant reserves of producible hydrocarbons, the developmentof more marginal fields will not be commercially attractive. Inaddition, there is a physical limit on the number of available riserslots at the top site facility.

The present invention aims to address this problem in order to enableproduction from more marginal satellite fields.

Viewed from a first aspect there is provided a modular, subseahydrocarbon production hub comprising a primary manifold and one or moreco-located extension structure(s), the primary manifold having firstconnections for connection to at least a riser and an umbilical from atop-side facility, and second connections for connection to at least oneextension structure, wherein at least one of the extension structure(s)comprises a secondary manifold having first connections connected to thesecond connections of the primary manifold, second connections forconnection to at least one further extension structure, and thirdconnections for connection to at least one wellhead or template, thesecondary manifold providing for a flow of produced hydrocarbon from theat least one wellhead or template to the top-side facility via theprimary manifold and the riser, and facilitating electrical and/orhydraulic control from the top-side facility via the primary manifoldand the umbilical.

The use of such a modular hub facilitates communication between a largenumber of subsea wells and the surface platform via a small number ofrisers and umbilicals. Furthermore, the modular configuration means thatif additional capacity or functionality is required, for example toproduce from new satellite wells or to provide additional subseaprocessing, then this can be provided simply by connecting furtherextension structures to the hub. For example, extension manifolds orprocessing equipment may be connected directly to on spare connectionson the primary manifold or an extension structure.

In the present context, the term “co-located” is intended to mean thatthe modular components of the hub (the primary manifold and theextension structures) are located in a group or cluster proximate oneanother in the context of an offshore hydrocarbon production facility,e.g. below a platform. Thus, they are proximate at least relative to asatellite well site, which will be remotely located, often tens ofkilometers away. In various embodiments, this could for example beunderstood to include components within the safety zone surrounding theriser (typically a 500 meter radius around the riser base, or primarymanifold in this case). More typically the components of the hub will becloser together and the distance between individual components wouldtypically be well under 100 m, and usually under 50 m. In someembodiments, the components may be directly adjacent and/or mechanicallyinter-connected (in addition to the fluid/control connections), e.g.bolted together or rigidly connected in some other manner.

In various embodiments, the primary manifold may provide connection tothe secondary manifold (or other extension structure) in respect of anyor all of the following services, which will typically connect to theriser: hydrocarbon production, water injection, gas injection, gas lift.Additionally (or alternatively) it may provide any or all of theservices provided via the umbilical, such as control, power and/orservice fluids (hydraulic, chemicals, barrier fluids).

Typically, the primary manifold will itself be connected to a wellheadand/or template and indeed, either or both manifolds may be connected toa plurality of wellheads and/or templates. Thus, the primary manifoldmay also have third connections for connection to at least one wellheador template. In some implementations, the hub may be installed at aninitial well site, and then expanded using extension structures toconnect subsea to new satellite sites as they are found or becomeviable.

The facilitation of control is preferably provided by the provision ofconduits and/or conductors within the riser/umbilical/connector thatdistribute one or more (and preferably all of) the following services:injection gas and water, electrical power, electrical control signals,communication, chemicals and/or hydraulic power. Corresponding conduitsand connections may then be provided within the primary manifold toallow distribution of these services to the secondary manifold(s). Mostpreferably, each of these services is provided to the hub.

Thus, by means of the invention, satellites can be added to the overallproduction system without any increase in the number of risers connectedto the top-side facility. Alternatively, where a large number ofsatellite fields are added, the increase in the number ofrisers/umbilicals is significantly reduced compared to the prior art.This minimises the number of topside modifications and reduces theoverall cost of producing from such satellite fields.

Preferably, the one or more extension structures include a plurality ofsecondary manifolds. As discussed above, the modular configurationpermits simple enlargement of the capacity of the hub to permit new wellsites to be connected and produced. The modular hub is not limited toany specific configuration, and in various embodiments at least two ofthe secondary manifolds may be connected to the primary manifold or toanother extension structure in series, i.e. as a daisy chain, or inparallel, e.g. in as spokes. The specific configurations available willof course depend upon the individual design of the components of the huband how many ports are available for the second connections on eachmodular component.

The hub, and particularly the primary manifold of the hub, preferablyalso provides valving arrangements so that flow of each of the variousproduction lines may be controlled. (Likewise, switching arrangementsmay be provided for electrical power, communications and control.) Thismay be necessary, either to open and close connection ports whensecondary manifolds are connected/disconnected, or for control purposesduring operation. Such valves may be remotely operated from the surface,automatically operated (e.g. safety cut-off systems) or operable by ROV.Preferably each conduit within the hub may be closed by means of a valveand preferably a valve is provided in association with each connectionport thereof.

The invention of course also extends to the hub when installed. Thus, ina second aspect, the present invention also provides a hydrocarbonproduction system comprising a top-side production platform connected bymeans of a riser and an umbilical to a hub on the sea floor as describedabove, the hub being in turn connected subsea to one or more wells,wherein hydrocarbons produced from each of the wells flow to theplatform via a secondary manifold of the hub, the primary manifold ofthe hub, and the riser, and wherein one or more of service fluids,electrical control signals, electrical power and injection fluids aretransmitted to each of the wells via first the primary manifold and thena secondary manifold.

It will therefore be seen that, in a particularly preferred embodiment,there is provided a production platform connected by means of a riserand an umbilical to a primary manifold on the sea floor. The primarymanifold is in turn connected to one or a plurality of secondarymanifolds that expand the capacity of the hub. The secondary manifoldsare themselves connected to wellheads and hydrocarbons produced fromthose wellheads flows via the secondary manifold, the primary manifoldand then, via a riser, to the platform. At the same time, fluid,electrical control signals, electrical power and/or injection fluids aretransmitted to the wellhead via first the primary manifold and then viathe secondary manifold.

Optionally, the primary manifold, a secondary manifold or one or more ofthe other extension structures may provide ancillary services. Suchservices may include: processing of produced fluids, such as separationof oil from water and/or gas, oil, gas and water treatment; boosting thefluid by means of a pump or compressor; measuring one or more of thedifferent fluid streams.

For example, an external pumping unit may be provided in an extensionstructure which may be used to increase the pressure of produced fluidsin order to maintain or increase the production from the satellitefield. The pumping unit may be connected to second connections of theprimary manifold or an extension structure.

In another example, one of the extension structures may comprise aseparator unit. The separator unit may be connected to secondconnections of the primary manifold or an extension structure. Theseparator unit may separate water from a hydrocarbon stream before thehydrocarbon stream is passed to the riser. This reduces the quantity ofwater raised unnecessarily to the surface. The separated water may bedischarged to sea or may be re-injected into a well. The separator unitmay additionally or alternatively separates a hydrocarbon gas phase froma hydrocarbon liquid phase. The gas phase can be used to provide gaslift. The liquid phase can be used as a driving medium for an ejector.Alternatively, the gas and liquid phases may be separated to facilitatepumping to the surface as separate phases, which may simplify thepumping equipment required.

Preferably, means is provided for connection of an externalpump/pressure module (to boost pressure of production from satellitefields). To achieve this, most preferably, the second connectionsinclude ports that are suitable both for connection to secondarymanifold and also for connection to such units.

Although the invention has been described in the context of both a riserand umbilical being provided between the top-side facility and thesubsea manifold, other aspects of the invention may involve only a riseror an umbilical, or pluralities of one or the other.

The invention also extends to a method of hydrocarbon productioncomprising the use of the system, or hub of any of the above aspects ofthe invention.

Viewed from a third aspect, the present invention also provides a methodof connecting a subsea wellhead to a top-side production platform via amodular, subsea hydrocarbon production hub connected to the platform viaa riser and an umbilical, the method comprising: connecting a secondarymanifold to the subsea hub; and connecting the wellhead subsea to theextension manifold of the hub such that hydrocarbons produced from thewellhead flow to the platform via the hub and the riser, and one or moreof service fluids, electrical control signals, electrical power andinjection fluids are transmitted to the wellhead via the hub and theumbilical.

In accordance with this method, a new satellite well or template can beadded to an existing subsea hydrocarbon production facility by simplyinstalling a modular extension structure to the hub and connecting thenew satellite to the extension structure. This avoids the need for newdedicated risers and umbilicals to be connected from the platform to thesite, thereby reducing costs and tie-offs required at the platform, andpotentially making new sites economically viable.

The method may further comprise (remotely) controlling a valvingarrangement and/or switching equipment within the hub to permit flow ofhydrocarbons and/or control to and from the new extension structure.

The method may further comprise connecting one of more functional unitsto the hub, for example to enable processing of the hydrocarbonsproduced by the satellite well. This may be required where the satellitewell has a different composition to existing wells and may requiredifferent processing to existing wells, e.g. a higher water or acid gascomposition or the like.

Embodiments of the invention will now be described, by way of exampleonly, and with reference to the accompanying drawings:—

FIG. 1 is a of view of a conventional system for producing hydrocarbonsfrom main and satellite fields;

FIG. 2 is schematic view of the first embodiment of the inventionshowing a primary manifold connected to two secondary manifolds and apumping unit;

FIG. 3 is a schematic view of another of embodiment of the inventionwhich differs from that of FIG. 2 in that a further pumping unit isshown in the position of one of the extension structures;

FIG. 4 is a schematic view of a still further embodiment in which aseparator is provided in connection with the primary manifold;

FIG. 5 a schematic diagram of a possible application of the invention toa complex oil field situation;

FIG. 6 is a schematic view of the network and valves in the primarymanifold;

FIG. 7 is a perspective view corresponding to FIG. 6;

FIG. 8 is a perspective view of a hub including the primary manifold anda pumping unit; and

FIG. 9 is a sectional view of an umbilical for use with the hubs of thevarious embodiments.

With reference to FIG. 2, there is shown a first embodiment of theinvention 20. A host platform 21, at the surface, is connected to asubsea hub 36, on the seabed, by means of risers and umbilicals 23.These correspond to the risers/umbilicals 5 in FIG. 1. Accordingly, theyprovide for control, power and fluids (hydraulic, chemicals and/orbarrier) (C), low pressure production (LP), high pressure production(HP) and injection of water (or gas) injection (WI). Gas lift may alsobe provided (not shown). The hub 36 comprises a primary manifold or“mother structure” 22 that receives the risers and umbilicals 23 fromthe surface. The primary manifold 22 is in turn connected to a pluralityof wells 24 (nos. 1, 2 and 3) by means of connectors 25, again similarlyto FIG. 1. These are shown as providing production (P), water injection(WI) and control (C), though any or all of the above-mentioned servicesmay also be provided.

The present embodiment 20 differs significantly from the prior artsystem shown in FIG. 1 in that the hub 36 has a modular configurationand can be extended after installation using extension structure thatincrease the capacity or capabilities of the primary manifold 22.

In FIG. 2, the hub 36 comprises two secondary or extension manifolds 26,30, which are examples of such extension structures. The first extensionmanifold 26 is connected to the primary manifold 22 by means ofconnections 27. The first extension structure 26 is adjacent to theprimary manifold 22, generally within about 50 meters and in some casesphysically adjoining the primary manifold 22 with preferably rigidconnections 27 The first extension manifold 26 provides connections towells 29 (nos. 4 and 5) by means of connections 28. These correspond toconnections 25 and 7, thus providing production P, water injection WIand control C, though any of the other above-mentioned services may beprovided.

The first extension manifold 26 is in turn connected to an adjacentsecond extension manifold 30 by means of connections 31, which can beidentical to connections 27. The second extension structure 30 is inturn connected to further satellite wells 32 by means of connections 33.

Only two extension manifold are shown in FIG. 2. However, it will beappreciated that a third extension manifold may be connected to thesecond extension manifold 30. Likewise further such structures may bedaisy-chained together, or connected in parallel.

In addition to being connected to the extension manifold, primarymanifold 22 is shown as being connected to a pumping unit 34 by means ofconduits 35. The pumping unit 24 is an extension structure that servesto pressurise the produced fluids to enable them to be transported tothe platform 21 in cases where one more of the produced wells is atinsufficiently high pressure.

As will be discussed further below, the primary manifold 22 andextension structures 26, 30, 34, have ports, which are used forconnection to various connectors, in a standard manner. Accordingly amodular system is provided whereby standardised extension structures,may be connected to the subsea hub 36 as desired.

The hub 36 thus provides for communication between a large number ofsubsea wells 24, 29, 32 and the surface platform 21 via a small numberof risers and umbilicals 23. If additional capacity or functionality isrequired, for example to produce from new satellite wells, then this canbe provided by simply connecting further extension manifolds or otherfunctional units to the hub 36.

The provision of additional subsea functionality is illustrated in FIG.3 where a second embodiment 40 is shown. This corresponds to the firstembodiment except that in place of second extension manifold 30, the hub36 is provided with a further pumping unit 41. Thus, the primarymanifold 22 is connected both to the second pumping unit 41 (indirectlyvia the first extension manifold 26) and to the first pumping unit 42.

Another example of the provision of additional subsea functionality isillustrated in FIG. 4, where the third embodiment 50 is shown. Thisdiffers from the second embodiment 40 in that, in place of first pumpingunit 42, the hub 36 is provided with a separator unit 51. The use of asubsea separator unit 51 permits improved efficiency of the hub in thisembodiment 50.

Produced hydrocarbons often contain substantial amounts of water. Thismay include formation water that was trapped in the reservoir, or waterinjected during production. The separator unit 51 separates water fromproduced fluids so that water is not wastefully transported to theplatform 52. This both relieves the riser, as a smaller quantity offluid must be transported to the surface, as well as reducing the amountof topside water processing required at the processing platform, wherespace is often limited. The water can be either discharged into the sea(subject to appropriate processing, for example using a furtherextension structure), or re-injected into an injection well.

As pure phases of liquid and/or gas are more controllable with respectto throttling, boosting and transporting than a two- or three phasemixture, the separator unit 51 can also separate liquid phase and gasphase hydrocarbons from one another. The gas phase may be pressurized asused as lift gas to increase production from a well. Alternatively or inaddition, the preferably gas-free liquid phase may be used as a drivingmedium for an ejector. Ejectors can be used to boost production of anexisting well or to restart a “dead” well.

Note that in any of FIGS. 2 to 4, the ancillary unit(s) may be providedin addition to the plural extension structures shown in FIG. 2; forclarity only a limited number of components are illustrated.

FIG. 5 shows a possible application of the invention to areas having anumber of hydrocarbon producing fields connected to the platform.

Here, production platform 61 is above the original well site and isconnected directly to the initial subsea template 62 in a conventionalmanner. Previously, the platform 61 would have been connected directlyto the satellite subsea templates 63 and 64 (for example, with referenceto FIG. 1, manifold 4 might have been at the initial site and riserbases 8, 9 and 10 might have been at satellite sites A, B and C).However, implementing the invention has the result that a subsea hub 65is instead provided in direct connection with the platform 61. Thesatellite templates 63 and 64 connect subsea to the hub 65, instead ofbeing connected directly to the platform.

This facilitates a reduction in the number of risers and umbilicalsrequired to connect these templates 63, 64 to the platform 61.Additionally, the invention enables satellite fields C, D, E, whichwould previously have been economically unviable, to be produced. Usingthe present invention, an extension manifold and any other requiredextension structures can be added to the hub 65, and productiontemplates 66, 67 and 68 can be installed and connected to the extensionmanifold of the hub 65. Field C is to be produced initially, with fieldsD and E being added later (hence they are shown in phantom).

The application of the invention to this oil field provides a number ofthe advantages described previously. In particular, there is a reducedneed for riser hang-offs at the production platform 61. It also makes iteasier to provide subsea water separation and pressure boosting, againas previously described. Furthermore, the use of a modular constructionpermits the capacity of the hub 65 to be increased to allow furthersatellite wells to be produced, without the need for new risers orumbilicals to directly connect the satellite well to the platform 61.

Details of the primary manifold and extension structures are describednow with reference to FIGS. 6 to 8.

Schematic pipework diagram 6 shows a hub 70 having a primary manifold71, an extension manifold 72 and a pumping unit 73. The physicalarrangement of the pipework and valves, etc. may be seen from FIGS. 7and 8.

The arrows at the upper part of FIG. 6 represent connections to theumbilical and riser which lead to the production platform. Produced oilis shown at 81 and 86, electrical control inputs at 82 and 83, waterinput at 84, and hydraulic control input at 85.

The connections to the various external units are shown at the lowerpart of the figure. Production input is at 87, 89 and 93, hydraulicfluid at 88 and 92, with water outlets at 90 and 91. It will also beseen that there are provided flow paths between each of the respectiveinputs and outputs and that control valves are provided in each line.

Connections 94 and 95 permit the connection of an external pump 73, withconnections 96, 97 and 98 providing injection water, hydraulic andproduction connections for future use.

Pumping unit 73 comprises an input and output conduit for connection tothe primary manifold 71, plus an internal pump and a control valve.

FIG. 8 shows the pipework of FIG. 7 mounted to a support cradle andconnected to the external pumping unit 73, thus corresponding to FIGS. 6and 7.

FIG. 9 illustrates a cross-section through an umbilical used to connectthe hub to the platform. It provides the following services:—

-   -   36× MEG tubes    -   6× low pressure hydraulic fluid tubes    -   6× high pressure hydraulic fluid tubes    -   6× chemicals tubes    -   2× barrier fluid tubes    -   4× spares hydraulic fluid tubes    -   33× FO cables    -   10× electrical quads (3-phase and earth)    -   4× spares electrical quads    -   2× HV triads 12 kV, 120 mm²

In use, the various control valves provided at the hub and elsewherewill normally be operated by remotely operated vehicles. However,certain safety critical valves may be controlled remotely and all bymeans of automatic operation based at the hub.

1. A modular, subsea hydrocarbon production hub comprising a primarymanifold and one or more co-located extension structure(s), the primarymanifold having first connections for connection to at least a riser andan umbilical from a top-side facility, and second connections forconnection to at least one extension structure, wherein at least one ofthe extension structure(s) comprises a secondary manifold having firstconnections connected to the second connections of the primary manifold,second connections for connection to at least one further extensionstructure, and third connections for connection to at least one wellheador template, the secondary manifold providing for a flow of producedhydrocarbon from the at least one wellhead or template to the top-sidefacility via the primary manifold and the riser, and facilitatingelectrical and/or hydraulic control from the top-side facility via theprimary manifold and the umbilical.
 2. A hub according to claim 1,wherein the second connections of the primary manifold provide servicesin respect of water injection and/or gas injection to the secondarymanifold.
 3. A hub according to claim 1, wherein the second connectionsof the primary manifold provide power to the secondary manifold.
 4. Ahub according to claim 1, wherein the primary manifold has thirdconnections for connection to at least one wellhead or template.
 5. Ahub according to claim 1, wherein each of the extension structures iswithin 500 meters, and preferably within 100 meters, of the primarymanifold.
 6. A hub according to claim 1, wherein the extensionstructures comprise a plurality of secondary manifolds.
 7. A hubaccording to claim 6, wherein at least two of the secondary manifoldsare connected to the primary manifold in series.
 8. A hub according toclaim 6, wherein at least two of the secondary manifolds are connectedto the primary manifold or to another secondary manifold in parallel. 9.A hub according to claim 1, wherein the primary manifold comprises avalving arrangement so that flow within various production lines of theprimary manifold may be controlled and/or a switching arrangement fordistribution of electrical power, communications and control.
 10. A hubaccording to claim 1, wherein one of the extension structures comprisesa service unit connected to the second connections of the primarymanifold or an extension structure, wherein the service unit provides anancillary service, and preferably provides one or more of the following:processing of produced fluids, such as separation of oil from waterand/or gas, oil, gas and water treatment; boosting of fluid by means ofa pump or compressor; and measuring the flow of one or more fluidstreams.
 11. A hub according to claim 1, wherein one of the extensionstructures comprises a separator unit connected to second connections ofthe primary manifold or an extension structure.
 12. A hub according toclaim 11, wherein the separator unit separates water from a hydrocarbonstream before the hydrocarbon stream is passed to the riser.
 13. A hubaccording to claim 11, wherein the separator unit separates ahydrocarbon gas phase from a hydrocarbon liquid phase, and optionallywherein the gas phase is used to provide gas lift and/or the liquidphase is used as a driving medium for an ejector.
 14. A hydrocarbonproduction system comprising a top-side production platform connected bymeans of a riser and an umbilical to a hub on the sea floor according toclaim 1, the hub being in turn connected subsea to one or more wells,wherein hydrocarbons produced from each of the wells flow to theplatform via a secondary manifold of the hub, the primary manifold ofthe hub, and the riser, and wherein one or more of service fluids,electrical control signals, electrical power and injection fluids aretransmitted to each of the wells via first the primary manifold and thena secondary manifold.
 15. A method of connecting a subsea wellhead to atop-side production platform via a modular, subsea hydrocarbonproduction hub connected to the platform via a riser and an umbilical,the method comprising: connecting a secondary manifold to the subseahub; and connecting the wellhead subsea to the extension manifold of thehub such that hydrocarbons produced from the wellhead flow to theplatform via the hub and the riser, and one or more of service fluids,electrical control signals, electrical power and injection fluids aretransmitted to the wellhead via the hub and the umbilical.